Elephant corridors in the Tarangire-Manyara Ecosystem are threatened by human development, which has fragmented habitat and intensified human-elephant conflict.

With GPS telemetry data from three bull elephants, researchers mapped the elephants’ habitat use and connectivity from 2006-2008 and compared it to data from 1960 using new analysis techniques.

The expansion of agriculture and villages decreased corridor connectivity and disrupted elephants’ movements, according to results of a circuit theory model.

A steady 3.2% increase in human population in Tanzania (Kiffner et al, 2015) has resulted in an expansion of agricultural land, pastoralism and village settlements.

The land-use changes in northern Tanzania’s Tarangire-Manyara Ecosystem (TME) have put local wildlife at risk. Wide-ranging animals have been forced into increasingly smaller home ranges, and wildlife movement into the newly developed areas can result in conflict with the new human residents. This conflict—in the form of crop or livestock raiding, and subsequent retaliation by farmers—sometimes has fatal results for both people and wildlife.

Clark University Graduate School of Geography student Yuka Fuchino worked with the help of her advisors Dr. John Rogan and Dr. Florencia Sangermano of Clark University and Dr. David Wilkie from the Wildlife Conservation Society to examine the effects of increased human development in the TME on the movement patterns of its largest, widest-ranging species, the African elephant (Loxodonta africana).

A young male elephant cools off at a small watering hole in Lake Manyara National Park. There are corridors connecting Lake Manyara to several protected areas. Photo credit: Danielle Bettermann.

The group analyzed GPS telemetry data retrieved from tracking collars placed on three bull elephants to map existing elephant corridors. Terrestrial corridors connect two or more habitat patches to allow animal movement from one to another (Jones et al, 2009). Knowing where animals move regularly can help inform land use planning in such a wildlife-rich region. The data was collected by the Tarangire Elephant Project, a WCS program that has been studying the elephants in the Tarangire ecosystem since 1993.

Fuchino said that the conflicts between humans and wildlife make the study of movement corridors important in conserving other species without substantially altering the humans’ lifestyle. With a population of over 4,000 elephants, the largest number in northern Tanzania, identifying these corridors in the TME is of great importance.

“With humans and wildlife competing for resources, there is increasing human-wildlife conflict that can result in human and wildlife fatalities,” Fuchino said. “Corridors are a mitigation technique to better the livelihoods of local communities by providing environment and ample space for wildlife to navigate from one habitat patch to another without affecting the livelihoods of the locals.”

Using GPS data to determine elephant corridors

Fuchino used data from GPS tracking collars collected by the Wildlife Conservation Society (WCS) from 2006 – 2008 to record and analyze the corridors traveled by three bull elephants, named Plato, Steager and Bancroft. According to Fuchino, previous wildlife corridor studies used interviews with local community members and conservation allies to determine important migratory areas.

With improved GPS tracking technology, researchers can use the elephants’ movements to understand habitat preferences and home range sizes.

Using a maximum entropy model, the researchers used the distribution of the GPS points to create a map of suitable habitats according to the elephants’ presence. The habitat suitability map was then used as a reference point for the circuit theory model, where areas of high habitat suitability would result in high connectivity between two areas, and low suitability represented poor connectivity. The model outputs showed which areas held the highest probability of an active corridor.

Fuchino said that at times the GPS would malfunction and not record the elephants’ coordinates, leaving holes in her data. Additionally, as the GPS recorded only the locations of the elephants, Fuchino said that not knowing the animals’ activities at each point was a drawback.

“…You lose the depth of the data because the researcher can’t observe how the elephant is interacting with the environment,” Fuchino said. “GPS [tracking] is great at accumulating data about exact locations, but we do not know what the elephants were doing in these locations.

In a previous study of corridor models in the TME, researchers applied logistic regression models to counts from aircraft-collected aerial elephant surveys and land cover data (Pittiglio et al, 2012). Fuchino was the first to analyze the elephants’ movement using tracking collar-collected data and the circuit theory model.

Altogether, Fuchino found seven corridors, two of which were not previously modeled by Pittiglio but were reported in the 1960s and 2000s. They connect Tarangire and Lake Manyara National Parks.

The importance of identifying corridors

A group of female elephants of different ages walk together in Tarangire National Park. Some of the historical corridors between Tarangire and Lake Manyara National Parks are blocked by agricultural areas. Photo credit: Danielle Bettermann.

African elephants are especially prone to human-wildlife conflict because of their large home ranges and affinity for certain crops (Hoare, 1999). Finding, preserving and creating elephant corridors is therefore of great importance in helping to maintain habitats suitable for movement and minimize human-elephant conflict.

“I know from reading other studies that some species have gone locally extinct in the Lake Manyara area because of the growing agricultural pressure,” Fuchino said. “Although elephants are not one of the locally extinct species, I am worried that it can be a possibility in the future.”

Through the circuit theory model, Fuchino was able to capture only the seven corridors that were not blocked by agricultural land, which are considered a barrier to movement. Consequently, corridors were shown through the circuit theory model with meandering paths that avoided human presence, and some connectivity through corridors identified in the 1960s was lost.

A family group of elephants forages in Manyara Ranch, northern Tanzania. The three collared elephants studied by Fuchino occupied Manyara Ranch for 30% of the total time that they spent in protected areas. Photo credit: Danielle Bettermann.

Maintaining movement corridors was particularly urgent in the Kwa Kuchinja corridor, which passes through the Burunge Wildlife Management Area (WMA), where settlements and agriculture blocks easy passage for elephants. In the Burunge WMA, the needs of both human livelihoods and wildlife are addressed according to community decisions, which has resulted in local extinction of several species as the human population grows.

“I hope that this research can provide evidence of the increasing influence that humans have on the natural landscapes and encourage conservation of ecologically important elephant corridors,” Fuchino said.

Fuchino is sharing her results with WCS, which has run a program in Tanzania since the 1950s that focuses on protecting the country’s natural landscape and biodiversity by providing incentives and benefits for cooperation of community members. She hopes that her study will assist WCS in making data-based decisions for the benefit of conservation.